This invention generally relates to the field of hydroenhancing surface properties of textile fabric by subjecting it to hydrojet treatment, and more particularly, to improving the efficiency of fabric hydroenhancement methods and equipment.
Prior hydroenhancement technology teaches that certain properties of woven or knitted fabrics, such as cover, yarn blooming, surface texture, hand, drape, etc., can be enhanced by impacting the surface of the fabric with rows of jet streams from a series of overhead manifolds as the fabric is conveyed on a support surface, as illustrated in FIG. 2, for example. Such conventional hydroenhancing equipment is described in greater detail in commonly-owned U.S. Pat. No. 4,967,456 of Sternlieb et al., issued on Nov. 6, 1990, entitled xe2x80x9cApparatus and Method For Hydroenhancing Fabricxe2x80x9d, which is incorporated herein by reference.
Generally, the conventional view has been that the degree of enhancement is related to the amount of energy imparted to the fabric. That is, the more energy delivered to the fabric, the more pronounced the enhancement effect. For example, U.S. Pat. No. 3,493,462 to Bunting teaches that the degree of surface treatment is related to the total energy E expended per weight of fabric in a pass under a hydrojet manifold, as calculated by the following equation:
xe2x80x83E=0.125 (YPG/sb), in hp.-hr./lb. of fabric,
where
Y=number of hydrojets (orifices) per linear inch of manifold,
P=pressure of fluid in the manifold, in p.s.i.g.,
G=volumetric flow of fluid in cu.ft./min. per orifice,
s=speed of passage of fabric under the-manifold, in ft./min., and
b=weight of fabric treated, in oz./sq.yd.
This equation provided by Bunting is a standard calculation used in the industry for energy expended in the hydrotreatment of a fabric.
The degree of enhancement imparted to the fabric can be measured in terms of the cover of the fibers in the fabric. Cover has an inverse relation to the air permeability of the fabric, which is measured in cu.ft./min./sq.ft. (cfm/ft2). The graph in FIG. 1 illustrates the relationship, as is known conventionally, between the total energy expended in hydrotreatment and the resulting air permeability property of the treated fabric. The graph shows that as the total energy expended (in hp-hr/lb) increases, the air permeability (in cfm/ft2) of the fabric decreases and, hence, the degree of enhancement, i.e., the cover of the fabric, increases.
Conventional equipment for hydroenhancing fabric has employed high-speed processing lines having one or more manifolds in parallel across the width of fabric conveyed in a machine direction on a conveyor, as shown in FIG. 2, for example. A fabric web 12 is advanced through a weft straightener 14, which aligns the fabric weft prior to processing, onto conveyor belt 22 driven on rollers 24. in a machine direction (arrow indicating a downstream direction) through a hydroenhancing station 16. A plurality of manifolds 30 are spaced apart and aligned in parallel extending in a cross direction (normal to the plane of the figure) across the width of the conveyed fabric. Each manifold has a row of jet orifices 32 which emit jets of water downwardly to impact on one side of the fabric 12. The belt 22 has a porous support surface (such as a wire or plastic mesh) for supporting the fabric while allowing fluid to drain down to a collector system 19. The opposite side of the fabric may be treated in the same run by another hydroenhancing station 18 having a drum conveyor 34 and a series of manifolds 30 spaced around the drum circumferentially. Following hydroenhancement, the fabric 12 is advanced to a tenter frame 20 for drying under tension to produce a uniform fabric of specified width. A more detailed description of such hydroenhancing equipment is provided in commonly-owned U.S. Pat. No. 4,1967,456 of Sternlieb et al., issued on Nov. 6, 1990, entitled xe2x80x9cApparatus and Method For Hydroenhancing Fabricxe2x80x9d, which is incorporated herein by reference.
Conventional techniques for obtaining suitable hydroenhancement of fabric include using high pressures of fluid jetted from the manifold, large-diameter jet orifices or lowered processing speeds to impact high energies of fluid per area of fabric per unit of time, and/or multiple manifold configurations. However, the requirements for handling high fluid pressures or fluid energies or multiple manifolds can increase the equipment size and complexity, as well as equipment and maintenance costs, significantly. The use of high total delivered energies, say in the range of 2.0 or 2.0 hp-hr/lb, is also less efficient, as improvements in fabric enhancement tend to taper off with further increases in energy. The use of high delivered energies can also cause greater fabric shrinkage, and can exacerbate the problem of interference patterns generated on the surface of the fabric by making traces of the jet streams more prominent in contrast to the yarn spacing in the fabric.
Hydroenhancement technology is related to technology for hydroentanglement or hydraulic needling of a web of fibers to produce autogenously bonded nonwoven fabric. In hydroentanglement technology, it has been the practice to obtain the desired degree of fiber entanglement with high energy input to the web of fibers. For the production of large quantities of hydroentangled fabric, large-scale, high-speed hydroentanglement lines and multiple-manifold equipment have been employed to deliver the needed hydroentanglement energies to continuously running webs. This type of large-scale equipment has also been used for hydroenhancement. However, it has a large capital cost which may only be justified for operations that can utilize very high output rates. For diversified product lines, the enhancement of different types of fabric in medium to small quantities requires equipment that is less capital intensive, adaptable to different fabrics, and more efficient to operate.
It is therefore a principal object of the present invention to improve the efficiency of fabric hydroenhancement by employing equipment that is smaller in size, can be adaptably configured for different types of fabrics, and delivers fluid energies for hydroenhancement in an optimized manner without wasting energy. It is a specific object of the invention to obtain comparable or even improved enhancement of fabrics with equipment that is greatly reduced in cost to build, operate, and maintain. A further object is to provide improved methods and equipment for fabric hydroenhancement that allow greater flexibility in making process adjustments for enhancing different types of fabrics and types of surface treatments. Still further objects of the invention include reducing warp yarn shrinkage and eliminating interference patterns in hydroenhancement of fabric.
In the present invention, the efficiency of fabric hydroenhancement can be improved by treating fabric with fluid jets at low levels of fluid energy per pass in multiple passes over the fabric. This can be carried out with compact equipment designed to simulate multiple passes on the fabric, which is of smaller scale and significantly reduced cost than conventional hydroenhancing equipment.
In a preferred embodiment of improved hydroenhancing equipment in accordance with the invention, referred to herein as xe2x80x9cjigging equipmentxe2x80x9d, a length of fabric is conveyed back and forth between a pair of unwind/windup reels on a sinuous path between a pair of manifolds for treating opposite sides of the fabric in multiple passes. The manifolds may be aligned at an angle to the vertical relative to support rolls supporting the fabric in order to allow convenient drainage of fluid away from the path of the fabric around the support rolls. This can eliminate the need for vacuum-suction removal of fluid. As an improvement to reduce equipment size, small-diameter solid support rolls may be used in treating certain type of fabrics.
The jigging equipment is configured to be self-contained and small in size. Only two manifolds are used to treat both sides of the fabric. This eliminates the need for the large and costly type of conventional processing lines that employ multiple manifolds and an extensive conveyor and fluid removal system for treating fabric in one continuous run. Suitable hydroenhancement of fabric can be obtained, for example, by conveying it back and forth 5 to 12 times (depending on fabric construction and the enhancement desired) between the reels with a manifold fluid pressure of 1800 psi. The total energy can be as low as 0.12 hp-hr/lb (0.062 hp-hr/lb per side). The low-energy, multiple-pass approach converts more of the delivered fluid energy to enhancement energy for greater efficiency and reduction in wasted energy, and also improves fabric coverage and reduces fabric shrinkage.
Other preferred embodiments of improved hydroenhancing equipment utilize a manifold or manifold system that is reciprocated, rotated, or oscillated relative to the fabric transport to simulate multiple passes on the fabric. In one version, a short section of manifold is reciprocated across or at an angle to the fabric travel direction to apply a jet curtain in overlapping swathes on the fabric in order to simulate multiple passes. The speed of reciprocating the manifold is selected relative to the fabric travel speed to obtain the desired number of passes per area of fabric per unit of time.
In another version of the improved hydroenhancement equipment, a pair of manifolds are coupled together and oscillated to simulate multiple passes on the fabric while conserving oscillation energy. The two manifolds can be arranged on the same side of the fabric to double the number of passes, or on opposite sides of the fabric for two-sided treatment in one run. The manifolds may be placed at an angle to the fabric travel direction (and warp yarns) for eliminating interference patterns in the fabric.
In another version, a plurality of jet strips are mounted on a rotating drum manifold to apply multiple jet curtains in overlapping swathes on the fabric in order to simulate multiple passes. The drum manifold may also be arranged at an angle to the fabric travel direction for eliminating interference patterns in the fabric. Each jet strip may be mounted in a jet module that is inserted in a cavity on the periphery of the drum and. held in place by pressure-fitting sealing strips.
As another feature of the invention, a manifold for the improved hydroenhancing equipment, of the type having a plenum for receiving input fluid under pressure and communicating through a row of distribution holes to an output end mounting a jet strip with jet orifices formed therein, has a baffle interposed downstream of the row of distribution holes and in close proximity to the jet strip for inducing turbulence in the fluid flow to cause the jets emitted from the jet orifices to have a constantly fluctuating cross-sectional shape, direction, and structure. For example, the resulting jets may be emitted as randomly spiralling ribbons. This results in distributing the delivered energy of the jets over a constantly changing impact area on the fabric for more efficient utilization of enhancement energy, and also improved enhancement of fabric including reducing or eliminating interference patterns in the fabric.
Another, combined-manifold embodiment of improved hydroenhancing equipment employs paired manifolds, with a downstream manifold having jets pointing vertically downward on the fabric and an upstream manifold having jets biased at an angle toward the fabric travel direction. The combined-manifold configuration results in improved utilization of delivered energy and fabric cover. A dense spacing of jets, or a double row of jets, may be used to eliminate interference patterns. The manifolds may also be angled across the fabric travel direction to eliminate interference patterns.
The low-delivered-energy, multiple-pass technique can also be implemented with conventional hydroenhancing equipment by increasing the process (line) speed to reduce the energy per pass delivered to the fabric and processing the fabric with multiple manifolds and/or in multiple runs. Good results have been obtained by operating a conventional line with multiple manifolds operated at conventional fluid pressures and energy levels but at high line speeds so that the delivered energy per side is lowered. Good enhancement with low energy delivered by multiple manifolds.
Other objects, features, and advantages of the present invention are described in further detail below, with reference to the following drawings: